1) Field of the Invention
Large highway vehicles such as semi-tractor trailers include rubber tired wheels which roll in contact with the road surface during forward travel. When these vehicles maneuver in confined spaces such as parking lots and loading dock areas they are often required to execute relatively tight turns. Typically the front wheels of these vehicles are steerable and therefore can turn to execute a vehicle turn. The other wheels of the semi or trailer typically are not adapted to turn in this manner, and therefore these other rear wheels can be dragged laterally across the pavement during execution of extremely tight turns. Friction between the wheel and the pavement causes the wheel to encounter large laterally directed forces during execution of a tight turn. These laterally directed friction forces cause the tires to wear, and can even cause the tread of the tire to be loosened or torn from the tires. Re-tread tires are especially susceptible to being torn apart by the lateral loads encountered by the tires during these small radius turns. The lateral friction forces and problems associated therewith are particularly acute in warm weather when friction between the warm tires and warm pavement is especially high. Pavement surfaces such as asphalt can also be damaged by the lateral dragging of semi tires during tight turns, especially in summer when the asphalt is warm and relatively soft.
2) Related Art
Several prior art devices have addressed problems associated with tires contacting the road surface. It is known in the prior art to spray tires with de-icing fluids which will help melt ice that has formed on the tires or roadway. These devices, such as that shown in U.S. Pat. No. 4,324,307, are designed to increase the friction between the tires and the roadway. Increased friction between the tires and road would only increase the damage to the tires and pavement surface when executing tight turns as described above.
In the railroad art it is known to lubricate the vertically extending flanges of train wheels as the train rounds a corner. The flanges tend to rub against the side edges of the rails as the train rounds a bend in the track, and the lubrication of the flange during turns decreases friction and generally prevents the flanges from wearing excessively. Patents such as U.S. Pat. No. 2,455,847 and U.S. Pat. No. 1,770,389 show such mechanisms. However, these references do not address the problem of lateral friction forces encountered by horizontal surfaces of wheels during execution of tight turns. Trains typically do not execute tight turns, since tracks are laid out so the train must execute only gradual turns. In this way the train can maintain relatively high speeds at all times with little risk of derailment. Because trains only execute gradual turns, the train's wheels generally do not encounter large lateral friction loads. Therefore, these railroad devices do not address or solve problems associated with laterally directed forces applied to wheels.
It would therefore be desirable to provide a mechanism which reduces tire wear of large highway vehicles caused during execution of tight turns of relatively small radius. It would be desirable to provide a mechanism which helps the tires resist failure when the tires encounter large lateral friction loads during tight turns. It would also be desirable for such a mechanism to help eliminate damage to paved surfaces caused by the laterally directed friction forces between the tires and the pavement during tight turns.